The signup process is very underhand. It's designed to trick you into allowing Nextdoor to use your name and identity to invite others, among other things. There is a way to avoid this but they make it hard to spot.
So you end up finding out a loat of other people have been invited using your name, without your knowledge. Letters sent out apparently from you.
And it goes on. Iniviter leader boards, prompts to allow postcards to invite others...
What you get for all this isn't worthwhile, and it's all so underhand I wonder if there is some purpose... maybe data collection for ads or something.
Essentially if you sign up they'll invite others in your name, to a site that - at best - has no worthwhile content. All very underhand and manipulative.
Got to wonder why they went to so much trouble.